A question I answered on Quora: What is best way to improve confidence for public speaking?

A:

Experience. Speak in public!!
Talk about a subject you A) Know well B) Care about deeply C) Have experience & credibility in. You need all 3.
Prepare you a** off. The better prepared you are, the less you need to think about when you step on the stage.
Join a Toastmasters club, whose sole purpose is helping each other improve. You can make mistakes and learn in a safe environment.
Dress well. That’s relative, so dress in a way in which you feel confident, which translates to how you'll perform.